It's been spam checked but was not detected as spam. The score (shown on the top line of this excerpt) can only be zero or 100 for basic checking which Plusnet implement. If it is zero (meaning not detected as spam) no Level header will be added.

One has to remember that spammers craft their emails in a way to avoid spam detection and filters have to adapt to keep up.

To help this process use webmail to report such messages as spam.

I received several messages of this type a while ago, initially not detected as spam but later they were. Now they've stopped. Fingers crossed that continues.

Re: Have they found a way to get round the spam filter

I very rarely receive any spam emails and yet over the past few weeks I have had dozens matching this description. I am now marking them as spam. The last one was tagged as spam but was not moved to the junk folder, although I have the setting ticked to do so. Please could someone tell me why it was not moved?

These emails are all addressed to my default email address plus two aliases. It is a domain address, not a Force 9 one. How do the spammers get the addresses? Seems odd that they have all three.

If you've had [-SPAM-] tagged messages delivered to your Inbox despite [your MMM] setting take a look at the Spam level shown in the message headers. I think you'll find such messages are Level 4 or 5 whereas your aggressiveness setting is 1 or 2.

Level 4 or 5 means the messages show slight spam indications but setting 1 or 2 means only those with higher spam indications are to go into the spam folder. So Level 4 or 5 go into Inbox.

It's a moot point whether the [-SPAM-] tag should be added to these, though it suits me for this to be done.

Changing aggressiveness to 5 in your MMM spam settings should ensure they are put in the Spam folder.

As Oldjim mentioned, reporting them as Spam in webmail should help improve detection accuracy.

Re: Have they found a way to get round the spam filter

Aggressiveness setting was 4 - now increased it to 5. The one that was tagged was level 5 so they now match. I haven't been marking them as spam but have now started to do this, with the result that the next one that came was tagged. Still wondering how the spammers have these addresses - strange that they have all three. Also, as there is obviously a lot of this type of message, can Plusnet now block them entirely?